This invention relates to coatings and more particularly to coatings on surfaces that are subjected to friction or wear and to coatings for tools utilized for cutting, forming and grinding.
In the past, tools and articles that are subject to wear have been fabricated to achieve various hardness, lubricity and wear characteristics by controlling certain parameters. For example, tools for working and shaping unhardened steels may be fabricated from steel containing enough carbon to form very hard martensite. In more complicated compositions, varying the carbon content and alloy content makes possible non-deforming steels, shock-resistant steels, hot-work steels, or high-speed steels. In some of these steels, alloying elements such as titanium, vanadium, molybdenum, tungsten and chromium are used. These are elements which have a great affinity for carbon and form hard, wear-resistant metallic carbides. However, in many cases, it it desirable to provide a tool having a coating on the surface thereof to improve the hardness and/or lubricity of the tool. This is especially the case where it is desired to lengthen the tool life or increase productivity, or where it is necessary to shape and work hardened steel, for example. However, many types of wear resistant coatings require high temperatures for application, thereby making them impractical for use on many types of substrate materials, since the properties of the substrate may change significantly under such temperatures. Other types of coatings do not adhere sufficiently to the substrate under working conditions.
Thus, a need exists for a wear resistant coating that can be applied at relatively low temperature to avoid significant change of substrate properties. A need exists for a wear-resistant coating for articles, such as tools, to provide increased life. A need also exists for a wear resistant coating that has improved adhesion properties and resistance to fracture.
In a more specific application, it would be desirable to provide an improved mold tool to lengthen mold tool life, improve release characteristics, and improve the surface finish and detail of molded items.